Emulsion polymers are prepared by the polymerization of unsaturated monomers using ionic- or free radical-initiated and propagated reactions. In addition to producing the desired polymer or polymers, the reaction generates detectable levels of unreacted by-products and leaves behind small amounts of unreacted monomer as well as saturated or unsaturated impurities present in the monomer; consequently, post-polymerization small-molecule residuals, in the form of unsaturated monomer, monomer by-products (e.g. saturated esters), and reaction by-products may create odor, instability, or toxicity. Subsequent reduction or elimination of these residual compounds has been disclosed. For example, residual unsaturated esters are known to be polymerized by heating for prolonged periods, with or without the addition of an ion- or a free radical-source; physical removal of residual unsaturated monomer by vacuum stripping and steam sparging is also known, as is conversion to less undesirable species by way of enzymatic hydrolysis.
For most polymers, saturated and unsaturated esters are not the only source of potential odor: Aldehydes, ketones, and alcohols, may each contribute to malodor in compositions, making their removal from the composition desirable or even necessary.
United States Patent No. US 2011/0166257 A1, (Bohling et al.) discloses a method for reducing residual ester levels and aldehydes, in particular, acetaldehyde in coating formulations. Bohling et al. discloses that residual esters and aldehydes can be reduced by treatment with a hydrolytic enzyme, particularly lipase or esterase, in combination with a nitrogen-containing nucleophilic molecule and/or sodium bisulfite. However, this disclosure does not discuss a method to assist in reducing alcohol content during the remediation of esters and aldehyde odorants.
Chinese patent No. CN 101353543A, also discloses enzymes for redox reactions in dry coatings for aldehyde abatement, specifically formaldehyde. However, this disclosure does not teach how to achieve effective aldehyde abatement.
It is therefore an object of this invention to provide stable aqueous polymer compositions with a conversion of VOCs, especially aldehydes and alcohols, to non-VOCs.